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Purification of cyclodextrin glucanotransferase (EC 2.4.1.19) from the culture liquid of Bacillus megaterium was carried out by the use of three purification procedures: (a) reverse osmosis and organic solvents precipitation, (b) ultrafiltration and gel-filtration chromatography, and (c) ultrafiltration, adsorption on starch, ion exchange chromatography and gel-filtration chromatography. Best precipitation was achieved by i-propanol - 85.92% of initial enzyme activity was preserved with purification of 1.47-fold. PS-20000 appeared to be the most suitable membrane for ultrafiltration. After 8.3-fold concentration by volume, the enzyme was purified 2.46-fold with a yield of 95.30%. As a result of the two-step purification procedure (ultrafiltration with membrane PS-20000 and gel-filtration chromatography) the enzyme was purified 36.2-fold with 95.45% of enzyme activity [measured in micrograms of cyclodextrins formed in 1 ml in 1 min under the assay conditions(U)] preserved. A highly purified enzyme preparation (purification of 74.56-fold and specific activity of 60.39 U/mg protein) was obtained by the third purification procedure. The purified enzyme preparation showed a single protein band on SDS-PAGE, 10% polyacrylamide gel. 相似文献
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Yamamoto T Fujiwara S Tachibana Y Takagi M Fukui K Imanaka T 《Journal of Bioscience and Bioengineering》2000,89(2):206-209
Cyclodextrin glucanotransferase (CGTase) from the hyperthermophilic archaeon Thermococcus sp. B1001 catalyzed the production predominantly of alpha-cyclodextrin (CD) from starch (Tachibana, Y. et al., Appl. Environ. Microbiol., 65, 1991-1997, 1999). The CGTase gene (cgtA) from this strain was cloned and sequenced. It was composed of 2217 nucleotides, and encoded a protein (739 amino acids) with a molecular mass of 83,240 Da. Recombinant CgtA expressed in Escherichia coli also catalyzed the production predominantly of alpha-CD from starch, as did native CgtA from strain B1001. Based on a substrate binding model of Bacillus circulans no. 8 CGTase, Tyr100, Trp191 and Tyr267 were specified to locate the spiral amylose and to minimize the size of the CD by saccharide aromatics interaction. In order to determine the critical residue for catalyzing production predominantly of alpha-CD, site-directed mutations were introduced in CgtA (Y100W, Tyr100-->Trp; W191Y, Trp191-->Tyr; W191F, Trp191-->Phe; Y267W, Tyr267-->Trp; Y267F, Tyr267-->Phe). Analysis of the reaction products by HPLC revealed that the mutant enzyme Y267W produced more beta- and gamma-CD than the wild-type enzyme. However, the other mutants still produced high levels of alpha-CD, suggesting that Tyr267 plays a critical role in alpha-CD production catalyzed by B1001 CGTase. 相似文献
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利用大肠杆菌Escherichia coli BL21(DE 3)克隆并表达来源于枯草芽孢杆菌Bacillus subtilis ATCC 15245的L-氨基酸连接酶(L-amino acid ligase,Lal)基因,采用Ni-NAT亲和层析法分离纯化得到重组的Lal,并以L-丙氨酸和L-谷氨酰胺为底物制备L-丙氨酰-L-谷氨酰胺(丙谷二肽).Lal属于ATP依赖酶,研究结果表明其最适反应温度和pH值分别为37℃和9.0,连续催化反应14 h可催化等摩尔的底物氨基酸(30 mmol/L)生成22.4 mmol/L的丙谷二肽,最高摩尔转化率可达74.7%.成功克隆表达了枯草芽孢杆菌的L-氨基酸连接酶,并将其应用于丙谷二肽的酶法合成,研究结果可为丙谷二肽的生物制造奠定理论基础. 相似文献
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2-花生四烯酸单甘酯(2-AG)是一种内源性大麻素,在神经、心血管和免疫等系统中具有一系列的生理活性。为实现2-AG的绿色高效制备,探究了脂肪酶催化醇解富含花生四烯酸的微生物油制备2-AG的方法。以2-单甘酯(2-MAG)含量为指标,通过单因素实验对酶法催化醇解反应条件进行了优化,并采用溶剂萃取法对产物进行纯化。结果表明:最佳反应条件为以Lipozyme 435脂肪酶为醇解脂肪酶、酶添加量4%(以油质量计)、油与无水乙醇物质的量比1∶40、叔丁醇为溶剂、油溶比2∶3、反应温度35℃、反应时间8 h,在最佳条件下粗产物中2-MAG含量为33.63%;经溶剂萃取纯化后2-MAG的纯度达到了94.79%,其中2-AG含量为40.70%。综上,酶法醇解富含花生四烯酸的微生物油可以获得高2-AG含量的2-MAG。 相似文献
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G. V. Chowdary & S. G. Prapulla 《International Journal of Food Science & Technology》2003,38(2):127-133
Summary Enzymatic synthesis of ethyl hexanoate by means of an acyl transfer reaction has been studied by using an immobilized Rhizomucor miehei lipase (RML). The effect of reaction parameters on ester synthesis has been investigated. Rhizomucor miehei lipase showed more specificity than other lipases when ethyl hexanoate was synthesized in n‐hexane. Maximum ester synthesis was obtained by using a 0.5 m substrate concentration (equimolar ratio). Temperatures in the range of 45–55 °C were found to be optimum and at higher temperatures (>60 °C) deactivation of enzyme was observed. Higher molar concentrations of hexanoic acid inhibited RML, but no inhibitory effect of ethyl caprate, even at higher molar concentrations, was observed. Apparent kinetic parameters have been determined. The values are as follows: KM (ester), 0.0135 m ; KM (acid), 0.08466; Ki (ester), 3.07 m ; Ki (acid), 0.550 m ; Vmax, 1.861 µmol min?1 mg?1 enzyme. 相似文献
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Sharma J Batovska D Kuwamori Y Asano Y 《Journal of Bioscience and Bioengineering》2005,100(6):662-666
Efficient selective synthesis of the secondary amide surfactant N-methyl lauroylethanolamide from methyl laurate and N-methylethanol amine by carrier-fixed Chirazyme L-2 (Candida antarctica) using a kinetic strategy has been demonstrated. When different solvents were screened for product yields using Chirazyme L-2, acetonitrile was found to be optimal. The rate of the reaction increased sharply by increasing the molar ratio of the reactants and the reaction temperature. When the reaction was performed at 50 degrees C for 36 h with 50 mmol ester and 100 mmol amine, the product was obtained in a 97.1% yield. With 50 mmol ester and 150 mmol amine, the highest yield (97.3%) was obtained after 16 h of incubation at 50 degrees C. It took only 5 h to get a yield of 95.8% at 60 degrees C using 50 mmol ester and 200 mmol amine. The enzyme activity in the amidation reaction mixture did not decrease notably even after six uses. 相似文献
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从大豆油脱臭馏出物中分别分离得到植物甾醇和脂肪酸,对植物甾醇的分离提取条件进行优化,确定甲醇-丙酮混合溶剂的比例为1:2 (V/V),溶剂原料比为3:1 (V/W),洗涤粗甾醇的溶剂为正己烷,分离出的脂肪酸主要为油酸、亚油酸等不饱和脂肪酸。通过物理吸附法固定CRL脂肪酶,考察不同载体固定脂肪酶的担载率和酶活力,确定大孔树脂HP20为最佳固定载体,酶活力最高且担载率最大。分离得到的植物甾醇和脂肪酸在固定化酶的催化作用下酯化合成植物甾醇酯,酯化率为45.11%,为日后各领域的应用提供了新的思路。 相似文献
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酶促反应合成蔗糖棕榈酸酯的研究 总被引:6,自引:0,他引:6
讨论了以Novozym 435脂肪酶为催化剂,以蔗糖和棕榈酸为底物的糖酯合成反应及其影响因素.考察了在丙二醇和正己烷存在下,底物酸糖摩尔比、含水量、温度、脂肪酶浓度、时间以及摇床速度对转化率的影响.实验结果表明,底物棕榈酸与蔗糖的摩尔比为1.2∶1.0、含水量为4%,反应温度为65℃、脂肪酶浓度为棕榈酸质量的4%、反应时间为4.5 h、摇床速度为200 r/min时,棕榈酸的转化率可达到86.94%. 相似文献
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Michael G. Gänzle 《International Dairy Journal》2012,22(2):116-122
Non-digestible oligosaccharides are applied as functional food ingredients to replace sucrose and to exploit specific biological functions, particularly low cariogenicity, low caloric content, prebiotic activity, and their ability to prevent adhesion of pathogens and toxins to eukaryotic cells. Oligosaccharides derived through enzymatic synthesis from lactose, i.e., galacto-oligosaccharides, lactulose and lactosucrose, account for a major part of the annual oligosaccharide production. Enzymatic production of oligosaccharides employs lactose as galactosyl-donor to transfer the galactosyl-moiety of lactose to suitable acceptor carbohydrates through the activity of β-galactosidases, or employs lactose as a galactosyl-, glucosyl- or fructosyl-acceptor through the activity of β-galactosidases, glucansucrases and fructansucrases. This communication provides an overview on the structural diversity of galacto-oligosaccharides and hetero-oligosaccharides that are produced by enzymatic conversion of lactose, and reviews the strategies used to optimize enzymatic transglycosylation with lactose as glycosyl donor or glycosyl acceptor. 相似文献
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为了满足市场对人工合成甘三酯的需求,研究以油酸和甘油为原料,在Novozym 435的催化作用下合成甘三酯,得到其最佳工艺条件为:反应温度100℃,底物甘油与油酸摩尔比1∶3,加酶量4%(以底物甘油和油酸总质量计),反应时间6 h,残压0.9×103Pa。在最佳工艺条件下,酯化度为94.36%±0.47%,产物中甘三酯含量为90.77%±0.85%。在最佳工艺条件下,酶重复使用9次,其催化活性无显著下降,酯化度、甘三酯含量分别为94.19%±1.70%、87.40%±2.62%;酶重复使用12次后,甘三酯含量仍能达到80%以上。经试验证实,该反应亦可推广应用于高酸值油脂的脱酸工艺中。 相似文献